Adult soft tissue and visceral sarcomas (excluding gastrointestinal stromal tumour) are rare tumours: Only 4–5 people out of 100 000 are diagnosed with STS per year in Europe. Overall, men have a slightly higher risk for STS than women and diagnosis occurs more frequently in patients >55 years, with the mean age at diagnosis being 59 years.

Soft tissue sarcomas often form in the body’s muscles, joints, fat, nerves, deep skin tissues, and blood vessels. They commonly affect the arms, legs and trunk, with the most frequent location being the limbs. Another significant proportion of cases are within the body - in the abdominal space, behind the retroperitoneum or in the female reproductive system.

Although the cause of most STS is unknown, there are known risk factors associated with the disease. These include genetic syndromes, radiation, and chemical exposure (e.g. herbicides and chlorophenols).

GIST

Gastrointestinal stromal tumor (GIST) affects the digestive tract or nearby structures within the abdomen. The most common location is the stomach. GI stromal tumor, or GIST cancer, is a sarcoma.